If I had to guess, I'd say we're a SE site that gets comparatively many questions that get marked as off-topic, mainly in the category of "shopping questions" and "usage questions".
From a comment of @Lundin, I've learned that
Stack Overflow is (having an attempt at) solving such issues by introducing a question entry wizard, which politely takes the asker through a set of questions. If the user clicks "I need a software recommendation", he's forwarded to the appropriate other SE site.
It guides people through sensible tag usage, and, even dearer to my heart, formulating good titles.
Can we have that, as a default for low and low-rep users (<110 pts), on this page, too?
For me, that would clearly make "be nice" easier. Instead of every time pointing out that, hey, asking for which device to buy, they could instead describe their problem and make this an interesting engineering question, that'd just be an instant close vote without a comment, because I'd know that these folks have gone through and ignored a wizard. There's really nothing that being helpful or welcoming can fix in that case. Instructions were clear; that leaves us with more time for the well-asked questions.
However, my hope is less negatively motivated: I think a well-designed wizard would not only deter off-topic questions, but it would encourage people to think about their problems in a productive, engineering-like way while or before asking them, making them better problems alltogether!